Growth and Destruction of PAH Molecules in Reactions with Carbon Atoms
Growth and Destruction of PAH Molecules in Reactions with Carbon Atoms
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DOI：
10.3847/1538-4357/836/1/32
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发表时间：
2017-02
期刊：
影响因子：
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通讯作者：
S. Krasnokutski;F. Huisken;C. Jäger;T. Henning
中科院分区：
文献类型：
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作者：
S. Krasnokutski;F. Huisken;C. Jäger;T. Henning
星际介质（ISM）中原子碳的丰度非常高，并且这些物质对包括苯在内的不同碳氢化合物分子具有高反应性，引发了有关多环芳烃（PAH）分子在太空中稳定性的问题。为了测试通过与原子碳反应破坏多环芳烃分子的效率，我们对萘、蒽和晕苯分子与基态碳原子的反应进行了一系列实验室和计算研究。该反应在 T = 0.37 K 的液氦液滴中通过量子化学计算进行了研究。我们的研究表明，所有小型和所有大型缩合多环芳烃都会与原子碳发生无势垒反应，因此应该在较宽的温度范围内通过此类反应有效破坏。同时，大而致密的围缩多环芳烃对这种反应应该更惰性。此外，考虑到其较高的光稳定性，在各种天体物理环境中，预期周围稠合多环芳烃的丰度应该高得多。碳原子和小 PAH 之间的无势垒反应也表明，在 ISM 中，这些反应可能导致 PAH 分子自下而上的形成。
A very high abundance of atomic carbon in the interstellar medium (ISM), and the high reactivity of these species toward different hydrocarbon molecules including benzene, raise questions regarding the stability of polycyclic aromatic hydrocarbon (PAH) molecules in space. To test the efficiency of destruction of PAH molecules via reactions with atomic carbon, we performed a set of laboratory and computational studies of the reactions of naphthalene, anthracene, and coronene molecules with carbon atoms in the ground state. The reactions were investigated in liquid helium droplets at T = 0.37 K and by quantum chemical computations. Our studies suggest that all small and all large catacondensed PAHs react barrierlessly with atomic carbon, and therefore should be efficiently destroyed by such reactions in a broad temperature range. At the same time, large compact pericondensed PAHs should be more inert toward such a reaction. In addition, taking into account their higher photostability, much higher abundances of pericondensed PAHs should be expected in various astrophysical environments. The barrierless reactions between carbon atoms and small PAHs also suggest that, in the ISM, these reactions could lead to the bottom-up formation of PAH molecules.